Migrating the master key is easy as long as you have the master key password, you just create that master key on the new instance OR you alter an existing master key on the new instance to include that password and you'll also need the certificate files, which you can either export from your existing instance or hopefully, you have a backup of somewhere.
--if there is no master key need to Create instead of alter
-- CREATE MASTER KEY ENCRYPTION BY PASSWORD = 'Master Key Password From Origin Instance'
ALTER MASTER KEY
ADD ENCRYPTION BY PASSWORD = 'Master Key Password From Origin Instance'
CREATE CERTIFICATE ORIGIN_EncryptCert
FROM FILE = 'C:\Program Files\Microsoft SQL Server\Backup\Origin_EncryptCert' --CERT FILE
WITH PRIVATE KEY
FILE = 'C:\Program Files\Microsoft SQL Server\Backup\Origin_EncryptCertKey.pvk', --KEYFILE
DECRYPTION BY PASSWORD = 'Cert Password from Origin Instance'